You'll want to look for the pre '92 S10 T-5s. Starting in 89/90 they went to electric speedometer. I just bought a 93 T5 and found out the hard way, it has a ford bolt pattern.
As far as rearend goes, you could try to find the coveted 4.11 gears out of 68-72 GM 3/4 ton trucks with automatic. Or you could swap the rearend out all together. I have a 14 bolt 63" wide rearend waiting to go under my 54. Some guys have had good luck with the Dana 60's too.
http://www.flatheadv8.org/ernie/ernie-t5.htm
